2005 Objectives Based National Building Code

Everything we wanted to know …

 By: Ken Rauch

Introduction

The 2005 Objectives-based NBC has been available for a few months now. I received my copy (two volumes) along with the insert outlining the warm-up and stretching exercises recommended before lifting it—it’s a big puppy! I spent some time browsing to understand where all the extra weight comes from.

Turns out that, unlike me, it’s not fat but muscle, and comes from new Sections that cross-reference the Code’s Acceptable Solutions (formerly called requirements) with the four Objectives on which the Code stands and a list of some 46 building functions (Functional Statements) that the Acceptable Solutions are intended to facilitate.

Why this Additional Information?

To paraphrase the Preface to the Code, spelling out the links between the Acceptable Solutions and the Code’s Objectives and Functional Statements is intended to facilitate the implementation of the Code by:

1. clarifying the Code’s intent for practitioners and officials and, hopefully, heading off disputes,
2. clarifying whether an Acceptable Solution applies in a given situation and
3. providing opportunities for alternative solutions that achieve the level of performance expected by the Code.

Not mentioned, but important, is the benefit to the consensus code-writing committees when considering changes or additions to the Code and to those charged with evaluating proposed alternative solutions. 

A Closer Look

At the end of each Part of the NBC we find a Section cross-referencing Acceptable Solutions with Objectives and Functional Statements.

All the Acceptable Solutions in Division B of the 2005 NBC are intended to support one or more of the following four Objectives (including some 53 sub-objectives):

-          safety of persons in or near buildings,

-          health of persons in or near buildings

-          accessibility to buildings for persons with disabilities, and

-          fire and structural protection for the buildings themselves.

Acceptable Solutions are intended to help allow buildings to perform one or more of 46 defined functions. These functions are listed in Sentence 3.2.1.1.1. of Division A under the heading (wait for it) Functional Statements. The Functional Statements that are primarily building-envelope-related are:

F51 – To maintain appropriate air and surface temperatures,

F52 – To maintain appropriate relative humidity,

F53 – To maintain appropriate indoor/outdoor air pressure differences,

F54 – To limit drafts,

F55 – To resist the transfer of air through environmental separators,

F61 – To resist the ingress of precipitation, water or moisture from the exterior or from the ground,

F62 – To facilitate the dissipation of water and moisture from the building, and

F63 – To limit moisture condensation.

If we take a look at some Acceptable Solutions, and examine the corresponding Functional Statements we can see pretty clearly what building-envelope-related function is expected.

Even More Information

The CD-ROM version of the Code, which will become available the spring of 2006, will include Intent Statements and Application Statements for each Code provision. These can be particularly useful when practitioners and officials discuss the acceptability of alternative solutions. The User’s Guide, on CD-ROM, which will also include the Intent Statements and Application Statements will be available this spring as well. For more information visit http://www.nationalcodes.ca/nbc/index_e.shtml.

Intent Statements show (sometimes in excruciating detail) the consequences an Acceptable Solution is intended to avoid and so offer an insight into what the provision is attempting to achieve.

Application Statements can be similarly useful by making it clear to what an Acceptable Solution applies.

A compelling reason to order the CD-ROM version of the Code is that navigating its interrelated elements will be infinitely easier than flipping back and forth among bookmarks as I was forced to do in the preparation of this article.

For the Whole Story

For those who have an unquenchable interest in this subject, the Preface to the NBC holds much more information on the structure of the new objective-based format than this brief article can. Part 2 of Division A of the NBC lists and explains the four Objectives on which the Code is based while Part 3 of Division A lists the functions a building or its elements are expected to perform.

About the Author

Ken Rauch is a building technologist with 23 years of service with Canada Mortgage and Housing Corporation in various technical and building code related positions in Manitoba and at CMHC’s National Office in Ottawa. Since 1997, he has assisted the Canadian Codes Centre, NRC with an Intent Analysis of the requirements National Building Code in preparation for the Objective-Based NBC. He makes his home in Cobourg, Ontario. Ken can be contacted by email at ken.rauch@sympatico.ca